APF Mark 90

Datasheet legend
Ab/c: Fractions calculation
AC: Alternating current
BaseN: Number base calculations
Card: Magnetic card storage
Cmem: Continuous memory
Cond: Conditional execution
Const: Scientific constants
Cplx: Complex number arithmetic
DC: Direct current
Eqlib: Equation library
Exp: Exponential/logarithmic functions
Fin: Financial functions
Grph: Graphing capability
Hyp: Hyperbolic functions
Ind: Indirect addressing
Intg: Numerical integration
Jump: Unconditional jump (GOTO)
Lbl: Program labels
LCD: Liquid Crystal Display
LED: Light-Emitting Diode
Li-ion: Lithium-ion rechargeable battery
Lreg: Linear regression (2-variable statistics)
mA: Milliamperes of current
Mtrx: Matrix support
NiCd: Nickel-Cadmium rechargeable battery
NiMH: Nickel-metal-hydrite rechargeable battery
Prnt: Printer
RTC: Real-time clock
Sdev: Standard deviation (1-variable statistics)
Solv: Equation solver
Subr: Subroutine call capability
Symb: Symbolic computing
Tape: Magnetic tape storage
Trig: Trigonometric functions
Units: Unit conversions
VAC: Volts AC
VDC: Volts DC
Years of production:   Display type: Numeric display  
New price:   Display color: Red  
    Display technology: Light-emitting diode 
Size: 6"×3"×1" Display size: 8+2 digits
Weight: 8 oz    
    Entry method: Algebraic 
Batteries: 3×"AA" NiCd Advanced functions: Trig Exp Hyp Lreg Units 
External power: APF 751S (7.5VDC 100mA)   Memory functions: +/-/×/÷ 
I/O:      
    Programming model: Keystroke entry 
Precision: 10 digits Program functions: Jump Cond  
Memories: 10 numbers Program display: Keycode display  
Program memory: 72 program steps Program editing: Overwrite capability  
Chipset: MOS Technologies   Forensic result: 9.14705679  

apf90.jpg (23293 bytes)The APF Mark 90 programmable calculator was yet another OEM variant of the Commodore PR-100. (Or was it the other way around?) However, unlike some of the other clones, this one looks quite different. Some of the buttons have different labels (e.g., STO), positions of the sliding program switch are rearranged, and the calculator's visual appearance matches that of other APF calculators of the LED era.

As it turns out, the differences are entirely cosmetic in nature. Internally, the two calculators are identical. A curious difference, however, does exist in the documentation: the Commodore PR-100 has a small manual that contains several example programs. The APF Mark 90's manual contains a number of interesting calculating examples, but none of them are presented in the form of a keystroke program.

The calculators may be identical, but I do have a new Gamma function implementation I wrote after I received this Mark 90. Unlike other implementations, this one does not use a polynomial approximation; instead, it evaluates the incomplete Gamma function. With an integration limit of 24 and an argument between 0 and 1, the result is essentially identical (within the calculator's limit of precision) to that of the Gamma function itself. The incomplete Gamma function is evaluated iteratively; for arguments greater than 1, another iteration is used to arrive at the final result. For most arguments, this program yields at least 8 digits of precision. The downside is that the program is a lot slower than a polynomial approximation.

85 00	−
81 01	1
51 02	STO
81 03	1
55 04	x/y
84 05	+
15 06	SKIP
14 07	GOTO
81 08	1
61 09	7
94 10	+/−
21 11	SHIFT
74 12	M×
81 13	1
14 14	GOTO
91 15	0
83 16	3
81 17	1
55 18	x/y
94 19	+/−
34 20	yx
51 21	STO
82 22	2
82 23	2
71 24	4    
55 25	x/y
75 26	÷
52 27	RCL
82 28	2
95 29	=
51 30	STO
71 31	4
51 32	STO
83 33	3
74 34	×
82 35	2
71 36	4
75 37	÷
81 38	1
21 39	SHIFT
84 40	M+
82 41	2
52 42	RCL
82 43	2
84 44	+
51 45	STO
83 46	3
52 47	RCL
71 48	4
85 49	-
21 50	SHIFT
55 51	x-M
71 52	4
55 53	x/y
95 54	=/K
94 55	+/−
52 56	RCL
15 57	SKIP
14 58	GOTO
83 59	3
83 60	3
71 61	4
75 62	÷
82 63	2
71 64	4
21 65	SHIFT
32 66	ex
74 67	×
52 68	RCL
81 69	1
95 70	=/K